The expression of glucose dehydrogenase (GO) is either monophasic or biphasic in various species within the genus Drosophila. The majority of species exhibit a single peak of GO activity (monophasic) during the pupal stage. Four subgroups within the melanogaster species group exhibit two peaks of GO activity: one peak during the pupal stages and one peak which is limited to the ejaculatory duct of males. The expression of male limited GO is correlated with a distinct ejaculatory duct morphology. GO has been shown to be required for the process of eclosion and is transferred from males to females during copulation in Drosophila melanogaster (one of the biphasic species). The primary objective of the proposed research is to elucidate the evolution of GO regulation in a few representative species within the genus Drosophila. Two monophasic species (D. pseudoobscura and D. takahashii) and two biphasic species (D. melanogaster and D. eugracilis) have been chosen for investigation. Three experimental methods will be used to examine GO regulation at various levels of control: DNA sequence analysis, gene transformation, and imaginal disc transplantation. Interspecific gene transformation and imaginal disc transplantation experiments will allow us to explore the GO regulatory differences in vivo. The combination of these two methods offers a novel approach to investigate the evolution of regulatory systems. In addition, the proposed research should add to our knowledge of how tissue and developmental specific factors control gene expression.